As the wireless network, such as 802.11/WLAN, 802.16/WiMAX, is widely available in the public network and enterprise network, the use of wireless network to provide packet switching voice, voice over IP, or multimedia services has become an inexpensive and convenient option for personal mobile communication.
The wireless network system is usually based on IP, and provides wireless network access through the extension of wireless network access point/base station. The core network includes one or more servers for assisting in establishing connections. The connections can be voice, video, or multimedia. The mobile node can communicate with the node in the internet.
However, the development of conventional applications was usually based on a fixed network, and rarely took the wireless network environment into account. For mobile nodes, the application usually assumes the operation in a wired network. When a mobile node switches between different networks, the application will change IP address because of the network interface switch or network environment change. That is, when a mobile node moves out of the home network into a foreign network, the mobile node must obtain a new IP address from the foreign network, which causes the interruption of the original connection.
If an internet application does not take the mobility management in a wireless network into account, the original connection may be interrupted when the mobile node switches between different networks. In this case, the user is required to re-establish the connection, or modifies/replaces application to support mobility management.
WIPO Patent No. WO0131472 disclosed a mobility management protocol for the third generation internet protocol (3G-IP) to support the real time and non-real time multimedia application on mobile nodes. The technology adopts and extends the Session Initiation Protocol (SIP) to provide the macro mobility of domain hand-off and sub-net hand-off so that a user can use the mobile node for network access at any place when the user is roaming in different 3G-IP networks.
This technology also supports transmission control protocol (TCP) application with mobility without changing TCP protocol. When a mobile node moves, the INVITE and INFO of SIP are used for IP binding and user identification. The REGISTER of SIP is used for obtaining a new IP address from dynamic host configuration protocol (DHCP) server. In the mean time, an agent called SIP_EYE is used for maintaining the TCP connection on the mobile platform.
This technology disclosed in the patent document supports SIP-based applications, but provides no solutions for general application. Also, when both ends of the 3G-IP environment are mobile nodes, this technology may not support simultaneous mobility.